scholarly journals A plastic collapse method for evaluating rotation capacity of full-restrained steel moment connections

2008 ◽  
Vol 35 (1-3) ◽  
pp. 191-214 ◽  
Author(s):  
Kyungkoo Lee ◽  
Bozidar Stojadinovic
Keyword(s):  
Low Cycle Fatigue ◽  
Plastic Hinge ◽  
Local Buckling ◽  
Collapse Mechanism ◽  
Plastic Collapse ◽  
Cycle Fatigue ◽  
Limit States ◽  
Plastic Hinges ◽  
Rotation Capacity ◽  
Degradation Failure

An analytical method to model failure of steel beam plastic hinges due to local buckling and low-cycle fatigue is proposed herein. This method is based on the plastic collapse mechanism approach and a yield-line plastic hinge (YLPH) model whose geometry is based on buckled shapes of beam plastic hinges observed in experiments. Two limit states, strength degradation failure induced by local buckling and low-cycle fatigue fracture, are considered. The proposed YLPH model was developed for FEMA-350 WUF-W, RBS and Free Flange connections and validated in comparisons to experimental data. This model can be used to estimate the seismic rotation capacity of fully restrained beam-column connections in special steel moment-resisting frames under both monotonic and cyclic loading conditions.

Experimental investigation into ultra-low cycle fatigue behavior of composite members in spatial grid structures

2020 ◽  
Vol 23 (12) ◽  
pp. 2514-2528
Author(s):  
Xiayun Song ◽  
Haiwang Li ◽  
Jie Zhang
Keyword(s):  
Energy Dissipation ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Plastic Hinge ◽  
Cumulative Damage ◽  
Cycle Fatigue ◽  
Plastic Hinges ◽  
Energy Dissipation Capacity ◽  
Spatial Grid

As earthquakes tend to cause ultra-low cycle fatigue failure of spatial grid structures in composite members and joints, this study sets out to test six groups of specimen comprising steel pipes and bolt sphere joints and analyzes the influence of joints and loading systems on failure modes, hysteretic behavior, skeleton curves, stiffness degradation, energy dissipation capacity, and the formation and development of plastic hinges. Results showed that the instability of the specimen in compressive loading led to the occurrence of denting and the formation of plastic hinges. Cracks originated in dented area, and ultra-low cycle fatigue fractures occurred in a dozen cycles. Plastic hinge was located in the middle area of the pipe, and the energy dissipation capacity was limited owing to the confined plastic hinge length. As the joint bending stiffness increased, so did the length of the plastic hinge, the degree of the dent, and the cumulative damage. Early fractures and a reduction in total energy consumption also occurred. Furthermore, a function related to the cumulative damage and macroscopic deformation that can evaluate the damage of the members in spatial grid structures was also established.

Reeled CRA Clad/Lined Pipeline Installation: Seastate Optimisation From Fatigue and Fracture Perspective

2018 ◽  
Author(s):  
Daowu Zhou ◽  
T. Sriskandarajah ◽  
Heidi Bowlby ◽  
Ove Skorpen
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Superposition Method ◽  
Cycle Fatigue ◽  
Limit States ◽  
Simplified Approach ◽  
Fatigue And Fracture ◽  
Girth Welds

The deformation mechanism in reel-lay of corrosive resistance alloy (CRA) clad/lined pipes can facilitate defect tearing and low cycle fatigue crack growth in the girth welds. Pipe-lay after straightening will subject the CRA welds to high cycle fatigue. The permissible seastate for installation will be governed by failure limit states such as local collapse, wrinkling of the liner, fatigue and fracture. By means of a recently completed offshore project in North Sea, this paper discusses seastate optimisation when installing pipelines with CRA girth welds, from a fatigue and fracture perspective. The additional limiting requirement in CRA welds to maintain CRA liner integrity can lead to significant assessment work since all critical welds shall be examined. AUT scanned defect data were utilised to maximise permissible seastates based on fatigue allowance from a fatigue crack growth calculation. An alternative simplified approach to derive the crack growth based on a superposition method is studied. It enables a straightforward real-time prediction of crack growth and has the potential to be used during the offshore campaign to improve the installation flexibility. Post-installation fracture assessment under more critical seastates is examined for CRA partial over-matching welds. A comparison of CDF between conventional ECA procedure and 3D FE is provided.

Failure Analysis of Thinned Wall Elbows Under Excessive Seismic Loading

2002 ◽  
Author(s):  
Masaki Shiratori ◽  
Yoji Ochi ◽  
Izumi Nakamura ◽  
Akihito Otani
Keyword(s):  
Finite Element ◽  
Fatigue Damage ◽  
Failure Modes ◽  
Low Cycle Fatigue ◽  
Local Buckling ◽  
Seismic Loading ◽  
Cycle Fatigue ◽  
Finite Element Analyses ◽  
Residual Thickness ◽  
Limited Period

A series of finite element analyses has been carried out in order to investigate the failure behaviors of degraded bent pipes with local thinning against seismic loading. The sensitivity of such parameters as the residual thickness, locations and width of the local thinning to the failure modes such as ovaling and local buckling and to the low cycle fatigue damage has been studied. It has been found that this approach is useful to make a reasonable experimental plan, which has to be carried out under the condition of limited cost and limited period.

Subsea Pipeline Lateral Buckling Design—Strain Concentration or Strain Capacity Reduction Factors

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
M. Liu ◽  
C. Cross
Keyword(s):  
Concentration Factor ◽  
Low Cycle Fatigue ◽  
Safety Margin ◽  
Local Buckling ◽  
Cycle Fatigue ◽  
Lateral Buckling ◽  
Strain Concentration ◽  
Strain Capacity ◽  
Global Strain ◽  
Capacity Reduction

A strain concentration factor is typically incorporated in the higher-pressure and high-temperature (HPHT) pipeline lateral buckling assessment to account for nonuniform stiffness or plastic bending moment. Increased strain concentration can compromise pipeline low cycle fatigue and lateral buckling capacity, leading to an early onset of local buckling failure. In this paper, the philosophy of local buckling mitigation using the strain concentration factor is examined. The local buckling behavior is evaluated. Global strain reduction and evolution against buckling are analyzed with respect to varying joint mismatch level. The concept of a strain reduction factor (SNRF) due to joint mismatch is developed based on the global strain capacity reduction with reference to the uniform configuration. It is demonstrated that the SNRF in terms of strain capacity reduction is a unique characteristic parameter. As opposed to strain concentration, it is an invariant insensitive to evaluation methods and design strain demand level, hence more representative as a limiting design metric to maintain the safety margin. The rationale for its introduction as an alternative to the strain concentration factor is outlined and its benefits are established. The method for obtaining the SNRF and its application is developed. The discernible difference and scenarios for application of either factor are discussed, including low and high cycle fatigue, linearity and stress concentration, engineering criticality assessment (ECA), and lateral buckling. Additional causal factors giving rise to mismatch such as pipe schedule transition and buckler arrestor are also discussed. Iterations of finite element (FE) analyses are performed for a pipe-in-pipe (PIP) configuration in a case study.

Low-Cycle Fatigue Test of Circular Concrete Filled Tubular Columns

2008 ◽  
Vol 400-402 ◽  
pp. 873-880 ◽  
Author(s):  
Guo Wei Zhang ◽  
Yan Xiao ◽  
Sashi K. Kunnath
Keyword(s):  
Fatigue Life ◽  
Large Scale ◽  
Low Cycle Fatigue ◽  
Plastic Hinge ◽  
Cumulative Damage ◽  
Cycle Fatigue ◽  
Deformation And Failure ◽  
Tubular Columns ◽  
Critical Components ◽  
Reversed Deformation

During earthquake, the inelastic action in the plastic hinge regions of structures and bridges results in significant reversed deformation and failure of the critical components because of cumulative damage. To simulate seismic behavior of structure members and develop a simplicity damage criterion for circular concrete filled steel tubular (CFT) columns subjected to a series of earthquake excitations, an experimental study was undertaken to investigate the cumulative damage and relationship between low cycle fatigue life and displacement amplitude. Two types of large scale circular CFT columns with different kinds of seam weld and inner concrete compressive strength including nine specimens were tested under quasi static loading with constant and variable cyclic amplitudes. The test data were evaluated with the fatigue model relating deformation and fatigue life. Fatigue life expressions for application in damage-based seismic design are developed.

Prediction of the fracture life of a wrinkled steel pipe subject to low cycle fatigue load

2007 ◽  
Vol 34 (9) ◽  
pp. 1131-1139 ◽  
Author(s):  
Sreekanta Das ◽  
J J. Roger Cheng ◽  
David W Murray
Keyword(s):  
Plastic Strain ◽  
Oil And Gas ◽  
Pipe Wall ◽  
Low Cycle Fatigue ◽  
Local Buckling ◽  
Petroleum Products ◽  
Assessment Model ◽  
Life Assessment ◽  
Cycle Fatigue ◽  
Fatigue Load

The economy of Canada depends largely on the performance of the hydrocarbon-based energy industry (oil and gas), which in turn is dependent on the performance of steel pipelines that are used for transporting crude oil, natural gas, and petroleum products. Field observations of buried pipelines indicate that it is not uncommon for geotechnical movements to impose large displacements on the pipelines, resulting in localized curvature, deformations, and strain in the pipe wall. Often these local deformations result in local buckling (wrinkling) in the pipe wall, and in the post-buckling range of response such wrinkles develop rapidly. Subsequent cyclic load histories may produce cyclic plastic strain reversals leading to the formation of fractures in the wrinkle region. This paper presents the development and application of a simple fracture-life assessment model that can be used successfully by the pipeline industries to assess the remaining life before fracture of wrinkled pipelines subject to strain reversals due to low cycle fatigue loadings.Key words: wrinkled pipeline, low cycle fatigue load, plastic strain reversal, fracture, hysteresis loop energy, fracture-life assessment model.

Subsea Pipeline Lateral Buckling Design: Strain Concentration or Strain Reduction Factors

2017 ◽  
Author(s):  
M. Liu
Keyword(s):  
Concentration Factor ◽  
Low Cycle Fatigue ◽  
Safety Margin ◽  
Local Buckling ◽  
Reduction Factor ◽  
Material Strength ◽  
Cycle Fatigue ◽  
Lateral Buckling ◽  
Strain Concentration ◽  
Global Strain

Strain based design is normally applied for HPHT pipelines when the conventional stress based method becomes impractical. In addition to a design safety factor, a strain concentration factor is typically incorporated in the lateral buckling assessment to account for non-uniform stiffness or plastic bending moment due to geometry and material strength mismatch between adjacent pipe joints. Increased strain concentration can compromise pipeline low cycle fatigue and lateral buckling capacity, leading to an early onset of local buckling failure. In this paper, the philosophy of local buckling mitigation using the strain concentration factor is examined. The local buckling behaviour is evaluated in relation to strain concentration. Global strain reduction and evolution against buckling is analysed with respect to varying joint mismatch level derived according to a structural reliability analysis. The concept of a strain reduction factor due to mismatch is developed and proposed based on the global strain capacity reduction with reference to the uniform configuration. It is demonstrated that the strain reduction factor is a unique characteristic parameter. As opposed to strain concentrations it is an invariant insensitive to evaluation methods and the design strain demand level, hence more representative as a limiting design metric to maintain the safety margin. The use of the strain reduction factor is thus put forward in strain based lateral buckling design as an alternative to using the strain concentration factor. The method for obtaining the strain reduction factor and its application is developed. The rationale for its introduction is outlined and some of its benefits are established. The discernible difference and scenarios for application of either factors are discussed, including low and high cycle fatigue, linearity and stress concentration (SNCF from SCF for welds), ECA and lateral buckling. Additional causal factors giving rise to mismatch such as pipe schedule transition and buckler arrestor are also discussed. Iterations of FE analyses are performed for a pipe-in-pipe configuration in a case study.

Effect of Local Wall Thinning on Low-Cycle Fatigue Behaviors of Elbow With Internal Pressure: Estimation of Fatigue Life Based on Revised Universal Slope Method

2013 ◽  
Author(s):  
Koji Takahashi ◽  
Kyohei Sato ◽  
Kazuya Matsuo ◽  
Kotoji Ando ◽  
Yoshio Urabe ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Internal Pressure ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Local Buckling ◽  
Cycle Fatigue ◽  
Slope Method ◽  
Wall Thinning ◽  
Local Wall Thinning

Low-cycle fatigue tests and finite element analysis were conducted using 100A elbow specimens made of STPT410 with local wall thinning in order to investigate the influences of local wall thinning on the low-cycle fatigue behaviors of elbows with internal pressure. Local wall thinning was machined on the inside of the elbow in order to simulate metal loss by flow-accelerated corrosion. The local wall thinning located in three different areas, called extrados, crown and intrados. Eroded ratio (eroded depth/wall thickness) was 0.5 and 0.8. The elbow specimens were subjected to cyclic in-plane bending under displacement control with internal pressure of 0 or 9 MPa. Fatigue failure was classified into two types. The one is the type of fatigue crack initiation and another is the type of crack initiation after local buckling. In the type of fatigue crack initiation, fatigue crack initiated at crown and propagates to the axial direction. In the type of crack initiation after local buckling, at first local buckling occurs and secondary, crack initiates at the same place and propagates to the circumferential direction. The low-cycle fatigue lives of elbows were predicted conservatively by the revised universal slope method.

scholarly journals Limit, Shakedown and Ratchet Analyses of Defective Pipeline Under Internal Pressure and Cyclic Thermal Loading

2011 ◽  
Author(s):  
Weihang Chen ◽  
Haofeng Chen ◽  
Tianbai Li ◽  
James Ure
Keyword(s):  
Plastic Strain ◽  
Internal Pressure ◽  
Low Cycle Fatigue ◽  
Strain Range ◽  
Collapse Mechanism ◽  
Cycle Fatigue ◽  
Matching Method ◽  
Plastic Strain Range ◽  
Fatigue Assessment ◽  
Linear Matching Method

In this study, the limit load, shakedown and ratchet limit of a defective pipeline subjected to constant internal pressure and a cyclic thermal gradient are analyzed. Ratchet limit and maximum plastic strain range are solved by employing the new Linear Matching Method (LMM) for the direct evaluation of the ratchet limit. Shakedown and ratchet limit interaction diagrams of the defective pipeline identifying the regions of shakedown, reverse plasticity, ratcheting and plastic collapse mechanism are presented and parametric studies involving different types and dimensions of part-through slot in the defective pipeline are investigated. The maximum plastic strain range over the steady cycle with different cyclic loading combinations is evaluated for a low cycle fatigue assessment. The location of the initiation of a fatigue crack for the defective pipeline with different slot type is determined. The proposed linear matching method provides a general-purpose technique for the evaluation of these key design limits and the plastic strain range for the low cycle fatigue assessment. The results for the defective pipeline shown in the paper confirm the applicability of this procedure to complex 3-D structures.

Sign in / Sign up

Export Citation Format

Share Document